Serum tumor markers enhance the predictive power of the AJCC and LCSGJ staging systems in resectable intrahepatic cholangiocarcinoma

Background: While several prognostic models have been developed to predict long-term outcomes in resectable intrahepatic cholangiocarcinoma (ICC), their prognostic discrimination remains limited. The addition of tumor markers might improve the prognostic power of the classification schemas proposed by the AJCC 8th edition and the Liver Cancer Study Group of Japan (LCSGJ). Methods: The prognostic discrimination of the AJCC and the LCSGJ were compared before and after the addition of CA 19-9 and CEA, using Harrell's C-index, net reclassification improvement (NRI) and the integrated discrimination improvement (IDI) in an international, multi-institutional cohort. Results: Eight hundred and five surgically treated patients with ICC that met the inclusion criteria were identified. On multivariable analysis, CEA5 ng/mL, 100IU/mL CA 19-9<500IU/mL and CA 19-9500 IU/mL were associated with worse overall survival. The C-index of the AJCC and the LCSGJ improved from 0.540 to 0.626 and 0.553 to 0.626, respectively following incorporation of CA 19-9 and CEA. The NRI and IDI metrics confirmed the superiority of the modified AJCC and LCSGJ, compared to the original versions. Conclusion: The inclusion of preoperative CA 19-9 and CEA in the AJCC and LCSGJ staging schemas may improve prognostic discrimination among surgically treated patients with ICC.